1. Field of the Invention
The present invention relates to an angle sensor having a drive pinion and two measuring pinions driven by the drive pinion in which the absolute angular position of the drive pinion can be determined from the absolute angular positions of the measuring pinions.
2. Background Art
EP 0 877 916 B1 (corresponding to U.S. Pat. No. 5,930,905) describes an angle sensor having a drive pinion and two measuring pinions driven by the drive pinion. The drive pinion is connected to a steering column. The pinions have a different number of teeth from one another. The sensor determines the absolute angular position of the steering column in a measurement region exceeding 360° (i.e., in a measurement range exceeding one full rotation of the steering column) by evaluating the beat angle according to the Nonius principle. The measuring pinions exhibit backlash from being engaged with the drive pinion which leads to hysteresis. Grease may be used to reduce the backlash. However, the elimination of backlash cannot be guaranteed over the operating temperature range and lifetime of the sensor.
EP 1 132 716 A1 (corresponding to U.S. Pat. No. 6,552,533) describes an angle sensor having a measuring pinion engaged without backlash to a drive pinion through a spring-loaded bearing. The sensor behaves the same way in the arrangements of EP 1 391 696 A2 (corresponding to U.S. Pat. No. 7,017,274). One arrangement pays for the elimination of hysteresis with a large measurement error as the measuring pinion and its axle to which a pickup element is coupled are thereby displaced with respect to the sensor axle. In the other arrangement, a safety problem can occur due to the indirect coupling of the measuring pinion as gear teeth can be jumped over as a result of the coupling flexibility.